Semiconductor memory device and method for operating the same

ABSTRACT

A semiconductor memory device includes an edge detector configured to receive two pairs of complementary clocks to detect edges of the clocks, a comparator configured to compare output signals of the edge detector to detect whether clocks of the same pair have a phase difference of 180 degrees and detect whether clocks of different pairs have a phase difference of 90 degrees, a control signal generator configured to generate a control signal for controlling phases of the clocks according to an output signal of the comparator, and a phase corrector configured to correct phases of the clocks in response to the control signal.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

The present invention claims priority of Korean patent applicationnumber 10-2007-0137430, filed on Dec. 26, 2007, which is incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor memory device, and moreparticularly to a phase correction circuit for correcting a phase of aclock signal of a semiconductor memory device to enhance operationreliability, and a phase correction method thereof.

In a system with a variety of semiconductor devices, a semiconductormemory device serves as a data storage. The semiconductor memory deviceoutputs data corresponding to addresses received from a data processor,e.g., a central processing unit (CPU), or stores data received from thedata processor into memory cells selected by addresses.

As the operating speed of the system increases and semiconductorintegrated circuit technologies are advanced, semiconductor memorydevices are required to input and output data at higher speed. To meetthis requirement, a synchronous memory device was developed. Thesynchronous memory device is designed to input and output data insynchronization with a received system clock.

However, since even the synchronous memory device could not meet therequired data input/output speed, a double data rate (DDR) synchronousmemory device was developed. The DDR synchronous memory device isdesigned to input or output data at falling edges and rising edges ofthe system clock.

The DDR synchronous memory device must process two data during one cycleof the system clock so as to input or output data at a falling edge anda rising edge of the system clock. In other words, the DDR synchronousmemory device must output data or input/store data at the rising edgeand the falling edge of the system clock. Specifically, the DDR memorydevice must output data exactly in synchronization with the rising edgeor the falling edge of the clock.

To increase operating speed of the semiconductor memory device, a quaddata rate (QDR) semiconductor memory device has been suggested. The QDRsemiconductor memory device is designed to transfer four data during onecycle of the system clock. Seeing that the typical DDR semiconductormemory device can transfer two data during one cycle of the systemclock, the QDR memory device can transfer up to two times more data thanthe typical semiconductor memory device in theory. The QDR memory deviceis different from the typical semiconductor memory device in that theQDR memory device uses two clocks, instead of using a single clock. Oneclock is used as a reference for transferring data, and the other clockis used as a reference for transferring addresses and commands forreading/writing the data, thereby increasing the speed ofreading/writing data. The QDR memory device can be widely applied tohigh-speed telecommunication and network apparatuses where the speed oftransferring data is more important than other factors such as powerconsumption, cost, and the like, and a graphic processing apparatusneeding to read and write a large amount of data in a short time.

When a system clock is applied to such a semiconductor memory device, aclock input buffer and a transfer line for transferring the system clockmay cause the system clock to be delayed and a phase of the system clockto be changed. To resolve this, the semiconductor memory devicegenerally includes a phase correction circuit for correcting a phase ofthe system clock. The phase correction circuit may also be used tocorrect a phase of a reference clock for transferring data to thesemiconductor memory device or to the outside. Specifically, thehigh-speed semiconductor memory device inputs/outputs data or addressesat both the rising edges and the falling edges of the reference clock.Therefore, a change in the phase of the reference clock may cause aninsufficient margin to the overall operations of the semiconductormemory device, and thus failure or delay of operations.

The phase correction circuit detects a phase of a clock and then delaysthe clock by a delay time to correct the detected phase of the clock. Ifthere is an error while detecting the phase, the error may decrease theaccuracy of the correction operation of the phase correction circuit.Such an error may be increased as the semiconductor memory device ishighly integrated and the operating speed of the semiconductor memorydevice is raised. Especially, as a line width of the circuit in thesemiconductor memory device becomes finer, the error may be increasedfurther. In addition, as a duty cycle of a clock received from theoutside is decreased, an error ratio, i.e., the ratio of the error tothe duty cycle of the clock, may be increased. The increase of the errorratio means that an operation margin of a read/write operation isdecreased, or that an accurate operation cannot be performed in apredetermined duration. Therefore, operation reliability of thesemiconductor memory device is decreased.

As described above, to allow the newly proposed QDR memory device toinput/output four data during one cycle of the system clock, the datashould be synchronized with phases of 0 degree, 90 degrees, 180 degrees,and 270 degrees of the system clock. In other words, the QDR memorydevice should output one data for each 90 degrees. As the data aresynchronized exactly with the phases of the system clock, each data canhave a maximum valid window for the operation of the semiconductormemory device, thereby enhancing the operation reliability of thesemiconductor memory device. Therefore, whereas the typicalsemiconductor memory device has a phase correction circuit formaintaining a phase distance of 180 degrees between a rising edge and afalling edge, the QDR memory device needs a phase correction circuit forcorrecting a phase of an internal clock so that data is transferredexactly at the phases of 0 degree, 90 degrees, 180 degrees, and 270degrees of the system clock.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to providing a phasecorrection circuit of a semiconductor memory device and a system, thephase correction, circuit using a quadrature phase clock to detect andcorrect phases of internal clocks corresponding to the quadrature phases(0 degree, 90 degrees, 180 degrees, and 270 degrees) of a system clock.

In accordance with an aspect of the present invention, there is provideda semiconductor memory device, which includes an edge detectorconfigured to receive two pairs of complementary clocks to detect edgesof the clocks, a comparator configured to compare output signals of theedge detector to detect whether clocks of the same pair have a phasedifference of 180 degrees and detect whether clocks of different pairshave a phase difference of 90 degrees, a control signal generatorconfigured to generate a control signal for controlling phases of theclocks according to an output signal of the comparator, and a phasecorrector configured to correct phases of the clocks in response to thecontrol signal.

In accordance with another aspect of the present invention, there isprovided a phase correction circuit, which includes a first detectorconfigured to detect whether a first clock and a second clock have aphase difference of 180 degrees, a second detector configured to detectwhether a third clock and a fourth clock have a phase difference of 180degrees, a phase detector configured to detect whether the first andthird clocks or the second and fourth clocks have a phase difference of90 degrees, a code counter configured to generate a plurality of digitalcodes corresponding to output signals of the first detector, the seconddetector and the phase detector, and a phase corrector configured tocorrect the first to fourth clocks in response to the plurality ofdigital codes to generate quadrature phase clocks.

In accordance with a further aspect of the present invention, there isprovided a phase correction method, which includes detecting a phasedifference between a first clock and a second clock to correct the firstand second clocks to have a phase difference of 180 degrees, detecting aphase difference between a third clock and a fourth clock to correct thethird and fourth clocks to have a phase difference of 180 degrees, anddetecting a phase difference between the first clock and the third clockto correct the first and third clocks to have a phase difference of 90degrees to generate quadrature phase signals.

In accordance with a further aspect of the present invention, there isprovided a clock phase correction method, which includes correcting Npairs of clocks (where, N is a natural number larger than 1) for oneclock of each pair to have a phase difference of 180 degrees with theother clock of the pair, and selecting one clock in each pair andcorrecting the selected clocks to have phase differences of 360/Ndegrees with each other to control all of the clocks to be separatedfrom each other by uniform phase differences of 360/N degrees.

In accordance with an aspect of the present invention, there is provideda phase correction circuit of a semiconductor memory device and a systemusing a quadrature phase clock to input or output two data in each logichigh section and two data in each logic low section of a system clock.The phase correction circuit corrects phases of internal clocks suchthat the internal clocks corresponding to the phases of 0 degree and 180degrees and the internal clocks corresponding to the phases of 90degrees and 270 degrees respectively have phase differences of 180degrees with each other. Thereafter, the phase correction circuitcorrects phases of the corrected internal clocks such that the correctedinternal clocks corresponding to the phases of 0 degree and 90 degreesand the corrected internal clocks corresponding to the phases of 180degrees and 270 degrees respectively have phase differences of 90degrees. Further, for the correction, the phase correction circuit liftsthe phase of the internal clock through a sequential step-by-stepprocess to remove error in the correction process and shorten thecorrection time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a phase correction circuit in accordancewith an embodiment of the present invention.

FIG. 2 is a block diagram of a phase correction circuit in accordancewith another embodiment of the present invention.

FIG. 3 is a timing diagram illustrating an operation of the phasecorrection circuit of FIG. 2.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, a phase correction circuit and a phase correction methodthereof in accordance with the present invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a phase correction circuit in accordancewith an embodiment of the present invention.

Referring to FIG. 1, the phase correction circuit of the semiconductormemory device includes an edge detector 120, a comparator 140, a controlsignal generator 180, and a phase corrector 190. The edge detector 120receives a pair of complementary clocks ICLK_O and IBCLK_O and a pair ofcomplementary clocks QCLK_O and QBCLK_O to detect edges having the samelogic level transition. The comparator 140 compares the detected edgescorresponding to the same pair of clocks, i.e., the clocks ICLK_O andIBCLK_O or the clocks QCLK_O and QBCLK_O, to determine whether theclocks of the same pair have a phase difference of 180 degrees. Thecomparator 140 also compares the detected edges corresponding todifferent pairs of clocks, i.e., clocks ICLK_O and QCLK_O or clocksIBCLK_O and QBCLK_O, to determine whether the clocks of different pairshave a phase difference of 90 degrees. The control signal generator 180outputs control signals IDCCON, QDCCON and QPCCON for phase correctionaccording to output signals of the comparator 140. The phase corrector190 corrects the phases of a pair of complementary clocks ICLK, IBCLKand a pair of complementary clocks QCLK and QBCLK according to thecontrol signals IDCCON, QDCCON and QPCCON, thereby outputting the fourclocks ICLK_O, IBCLK_O, QCLK_O and QBCLK_O. The four clocks ICLK, IBCLK,QCLK and QBCLK are input to the phase corrector 190 as initial valuesand then the four clocks ICLK_O, IBCLK_O, QCLK_O and QBCLK_O are fedback for the correction (not shown).

The edge detector 120 includes a first edge detector 122 and a secondedge detector 124. The first edge detector 122 detects rising edges of afirst clock ICLK_O and a second clock IBCLK_O. The second edge detector124 detects rising edges of a third clock QCLK_O and a fourth clockQBCLK_O.

The comparator 140 includes a first duty detector 142, a second dutydetector 144, and a phase detector 146. The first duty detector 142compares a duty ratio difference between output signals I_EDGE andIB_EDGE of the first edge detector 122. The second duty detector 144compares a duty ratio difference between output signals Q_EDGE andQB_EDGE of the second edge detector 122. The phase detector 146 comparesan output signal of the first edge detector 122 with an output signal ofthe second edge detector 124 to determine whether the different pair ofclocks have a phase difference of 90 degrees therebetween.

As circuit configuration in accordance with embodiments of the presentinvention, the control signal generator 180 may output the controlsignals having analog values or digital value. In the case when thecontrol signals IDCCON, QDCCON and QPCCON generated in response tooutput signals of the comparator 140 are analogue signals having voltagelevels, the phase corrector 190 includes a voltage-controlled delay line(VCDL) capable of changing delay times according to the analogue controlsignals. On the contrary, in the case when the control signals IDCCON,QDCCON and QPCCON are digital signals, the phase corrector 190 includesa plurality of shift registers capable of changing delay times accordingto the digital control signals.

The phase correction circuit of the semiconductor memory device furtherincludes a sequence controller 110 for controlling the comparator 140and the control signal generator 180. The sequence controller 110operates the first and second duty detectors 142 and 144 and a phasedetector 146 of the comparator 140 step-by-step such that a phasedifference between clocks of different pair is corrected to 90 degreesafter a phase difference between clocks of the same pair is corrected to180 degrees.

FIG. 2 is a block diagram of a phase correction circuit in accordancewith another embodiment of the present invention.

Referring to FIG. 2, the phase correction circuit includes a firstdetector 220, a second detector 240, a phase detector 260, a codecounter 280, and a phase corrector 290. The first detector 220 detects aphase difference between a first clock ICLK_O and a second clockIBCLK_O. The second detector 240 detects a phase difference between athird clock QCLK_O and a fourth clock QBCLK_O. The phase detector 260detects whether a phase difference between the first and third clocksICLK_O and QCLK_O or the second and fourth clocks IBCLK_O and QBCLK_O is90 degrees. The code counter 280 outputs a plurality of digital codesICODE<0:N−1>, QCODE<0:N−1> and QPCCODE<0:N−1> corresponding to outputsignals of the first and second detectors 220 and 240 and the phasedetector 260. The phase corrector 290 corrects phases of first to fourthinput clocks in response to the plurality of digital codes ICODE<0:N−1>,QCODE<0:N−1> and QPCODE<0:N−1> to generate quadrature phase clocks,i.e., the first to fourth clocks ICLK_O, IBCLK_O, QCLK_O and QBCLK_O. Asdescribed in reference to FIG. 1, clocks ICLK, QCLK, IBCLK and QBCLK areinput to the phase corrector 190 as initial values and then the first tofourth clocks ICLK_O, IBCLK_O, QCLK_O and QBCLK_O are fed back for thecorrection (not shown). In the result, the first to fourth clocksICLK_O, QCLK_O, IBCLK_O and QBCLK_O are separated by phase differencesof 90 degrees therebetween, and are mainly used in a semiconductormemory device (quad data rate memory device: QDR), telecommunication andnetwork system that can transfer four data during one cycle of thesystem clock.

The first detector 220 includes a first edge detector 222 for detectinga rising edge of the first clock ICLK_O and a rising edge of the secondclock IBCLK_O, and a first duty detector 224 for detecting a duty ratiodifference between the output signals of the first edge detector 222.Similarly, the second detector 240 includes a second edge detector 242for detecting a rising edge of the third clock QCLK_O and a rising edgeof the fourth clock QBCLK_O, and a second duty detector 244 fordetecting a duty ratio difference between the output signals of thesecond edge detector 222.

The first edge detector 222 in the first detector 220 activates a firstedge detection signal I_EDGE and deactivates a second edge detectionsignal IB_EDGE in response to the rising edge of the first clock ICLK_O.Also, the first edge detector 222 deactivates the first edge detectionsignal I_EDGE and activates the second edge detection signal IB_EDGE inresponse to the rising edge of the second clock IBCLK_O. The first dutydetector 224 compares durations of logic high level sections of thefirst edge detection signal I_EDGE and the second edge detection signalIB_EDGE. When the duration of the logic high level section of the firstedge detection signal I_EDGE is longer than the duration of the logichigh level section of the second edge detection signal IB_EDGE, thefirst duty detector 224 activates a first comparison signal IDCDOUT. Onthe contrary, when the duration of the logic high level section of thesecond edge detection signal IB_EDGE is longer than the duration of thelogic high level section of the first edge detection signal I_EDGE, thefirst duty detector 224 activates a second comparison signal IDCDSTB.

Then, the code counter 280 outputs a first delay control codeICODE<0:N−1> to the phase corrector 290 in response to the first andsecond comparison signals IDCDOUT and IDCDSTB received from the firstduty detector 224. To this end, the code counter 280 is provided with anN-bit counter (where, N is a natural number) to increase or decrease avalue of the first delay control code ICODE<0:N−1> according to thefirst and second comparison signals IDCDOUT and IDCDSTB.

The phase corrector 290 delays phases of the first and second inputclocks ICLK and IBCLK by a phase delay time corresponding to the firstdelay control code ICODE<0:N−1> and outputs first and second correctedclocks, i.e., the first and second clocks ICLK_O and IBCLK_O, having aphase difference of 180 degrees therebetween. Here, the phase corrector290 includes a signal transfer line with a plurality of delays forchanging phases of the input clocks ICLK, QCLK, IBCLK and QBCLK. Thephase corrector 290 controls the number of the delays through which thefirst and second clocks pass, according to the first delay control codeICODE<0:N−1> of N bits output from the code counter 280.

The second edge detector 242 in the second detector 240 activates athird edge detection signal Q_EDGE and deactivates a fourth edgedetection signal QB_EDGE in response to the rising edge of the thirdclock QCLK_O. Also, the second edge detector 242 deactivates the thirdedge detection signal Q_EDGE and activates the fourth edge detectionsignal QB_EDGE in response to the rising edge of the fourth clockQBCLK_O. The second duty detector 244 compares durations of logic highlevel sections of the third edge detection signal Q_EDGE and the fourthedge detection signal QB_EDGE. When the duration of the logic high levelsection of the third edge detection signal I_EDGE is longer than theduration of the logic high level section of the fourth edge detectionsignal IB_EDGE, the second duty detector 244 activates a thirdcomparison signal QDCDOUT. On the contrary, when the duration of thelogic high level section of the fourth edge detection signal IB_EDGE islonger than the duration of the logic high level section of the thirdedge detection signal I_EDGE, the second duty detector 244 activates afourth comparison signal QDCDSTB.

Then, the code counter 280 outputs a second delay control codeQCODE<0:N−1> to the phase corrector 290 in response to the third andfourth comparison signals QDCDOUT and QDCDSTB. To this end, the codecounter 280 is provided with an N-bit counter (where, N is a naturalnumber) to increase or decrease a value of the second delay control codeQCODE<0:N−1> according to the third and fourth comparison signalsQDCDOUT and QDCDSTB.

The phase corrector 290 delays phases of third and fourth input clocksQCLK and QBCLK by a phase delay time corresponding to the second delaycontrol code QCODE<0:N−1> and outputs third and fourth corrected clocks,i.e., the third and fourth clocks QCLK_O and QBCLK_O, having a phasedifference of 180 degrees therebetween.

As described above, the phase correction circuit corrects the phases ofthe four input clocks ICLK, IBCLK, QCLK, and QBCLK such that the firstand second clocks ICLK_O and IBCLK_O have a phase difference of 180degrees, and the third and fourth clocks QCLK_O and QBCLK_O have a phasedifference of 180 degrees. To this end, in the case of the first andsecond input clocks ICLK and IBCLK, the phase correction circuitperforms a phase delay operation and the delay time is determinedaccording to the comparison result between the phases of the first andsecond clocks ICLK_O and IBCLK_O. The operation result is fed back torepeat the operation until the phase difference between the first andsecond clocks ICLK_O and IBCLK_O becomes exactly 180 degrees. If both ofthe first and second comparison signals IDCDOUT and IDCDSTB aredeactivated, it is determined that the phase difference between thefirst and second clocks ICLK_O and IBCLK_O is exactly 180 degrees. Then,the value of the delay control code ICODE<0:N-1> is not changed anymore. Phase comparison and delay operations are also performed on thethird and fourth input clocks QCLK and QBCLK in a similar way asdescribed above until the phase difference between the third and fourthclocks QCLK_O and QBCLK_O becomes exactly 180 degrees.

After correcting the clocks ICLK_O, IBCLK_O and the clocks QCLK_O andQBCLK_O to have phase differences of exactly 180 degrees, respectively,the phase detector 260 receives the output signals of the first edgedetector 222 and the second edge detector 242 to determine whether theclocks ICLK_O and QCLK_O or the clocks IBCLK_O and QBCLK_O have a phasedifference of 90 degrees. In more detail, the phase detector 260 mixesthe first edge detection signal I_EDGE received from the first edgedetector 222 and the third edge detection signal Q_EDGE received fromthe second edge detector 242. The phase detector 260 also mixes thesecond edge detection signal IB_EDGE received from the first edgedetector 222 and the fourth edge detection signal QB_EDGE received fromthe second edge detector 242. Then, the phase detector 260 determineswhether the phase difference between the clocks ICLK_O and QCLK_O or theclocks IBCLK_O and QBCLK_O is 90 degrees by detecting whether the twomixed signals have a phase difference of 180 degrees with each other.The output signals QPDOUT and QPDSTB of the phase detector 260 aresimilar to the output signals of the first duty detector 224 and thesecond duty detector 244. The code counter 280 increases or decreasesthe value of a third delay control code QPCCODE<0:N−1> according to theoutput signals QPDOUT and QPDSTB of the phase detector 260. The phasecorrector 290 controls phase delay times for the first and third inputclocks ICLK and QCLK to output the first and third corrected clocks,i.e., the first and third clocks ICLK_O and QCLK_O, having a phasedifference of 90 degrees therebetween.

As described above, the phase corrector 290 includes a plurality ofdelays for delaying the first to fourth input clocks ICLK, QCLK, IBCLKand QBCLK to output the first to fourth corrected clocks ICLK_O, QCLK_O,IBCLK_O and QBCLK_O as quadrature phase clocks. The phase delay times ofthe first to fourth input clocks ICLK, QCLK, IBCLK and QBCLK aredetermined according to the first and third delay control codesICODE<0:N−1>, QCODE<0:N-1> and QPCCODE<0:N−1>.

The phase correction circuit further includes a sequence controller 210.The sequence controller 210 generates a first enable signal IDCD_EN forenabling the first duty detector 224, a second enable signal QDCD_EN forenabling the second duty detector 244, and a third enable signal QPD_ENfor enabling the phase detector 260. Here, the sequence controller 210outputs the first to third enable signals IDCD_EN, QDCD_EN and QPD_EN tothe code counter 280 to control each of the N-bit counters in the codecounter 280. Here, the third enable signal QPD_EN is activated after thefirst enable signal IDCD_EN and the second enable signal QDCD_EN aredeactivated.

The code counter 280 includes a plurality of N-bit counters, each ofwhich converts the output signal of the first duty detector 224 to thefirst delay control code ICOD<0:N−1> when the first enable signalIDCD_EN is activated, converts the output signal of the second dutydetector 244 to the second delay control code QCODE<0:N−1> when thesecond enable signal QDCD_EN is activated, and converts the outputsignal of the phase detector 260 to the third delay control codeQPCCODE<0:N-1> when the third enable signal QPD_EN is activated.Therefore, the phase correction circuit in accordance with thisembodiment can perform the operations for generating quadrature phaseclocks sequentially and selectively, to prevent a malfunction and reducecurrent consumption.

The first to third enable signals IDCD_EN, QDCD_EN and QPD_EN may bedesigned to be activated for predetermined durations after the receiptof the driving signal START_UP. Though not shown, the first to thirdenable signals IDCD_EN, QDCD_EN and QPD_EN may be designed to beactivated or deactivated in response to the output signals of the firstduty detector 224, the second duty detector 244, and the phase detector260.

Since operations of the circuit are sufficiently described above andcircuits for performing the operations can be easily implemented with avariety of designs by those skilled in the art, a detailed descriptionthereof will be omitted. The phase correction circuit in accordance withembodiments of the present invention can be applied to any system orelectronic apparatus that uses four quadrature phase clocks I, Q, /I and/Q having different phases. The phase correction circuit performs thefollowing operations to make the phase differences of the quadraturephase clocks uniform. First, the phase correction circuit correctsphases of the clocks of the same pairs (i.e., clocks I and /I, andclocks Q and /Q) to have phase relation corresponding 0 degree and 180degrees or phase relation corresponding 90 degrees and 270 degrees,respectively. Next, the phase correction circuit performs a quadraturephase correction on one clock of each pair of clocks to establish aphase relation of 0 degree and 90 degrees between the clocks ofdifferent pairs. Resultantly, rising edges of the four quadrature phaseclocks I, Q, /I and /Q can have exact phase relations of 0 degree, 90degrees, 180 degrees and 270 degrees.

FIG. 3 is a timing diagram illustrating an operation of the phasecorrection circuit of FIG. 2.

Referring to FIG. 3, the phase correction circuit generates quadraturephase clocks by performing two main operations. The first main operationincludes correcting phases of a pair of clocks I and /I to establish aphase relation of 0 degree and 180 degrees therebetween, and correctingphases of another pair of clocks Q and /Q to establish a phase relationof 90 degrees and 270 degrees therebetween. The second main operation isperforming quadrature phase corrections on the clock I of the pair ofclocks I and /I and the clock Q of the pair of clocks Q and /Q toestablish a phase relation of 0 degree and 90 degrees between the clockI and the clock Q. In other word, it is assumed that first to fourthclocks ICLK, QCLK, IBCLK and QBCLK have inappropriate phases in aninitial state. When the first main operation is performed, the firstclock ICLK and the second clock IBCLK come to have a phase difference of180 degrees, and the third clock QCLK and the fourth clock QBCLK alsocome to have a phase difference of 180 degrees. However, the phasedifference between the first clock ICLK and the third clock QCLK is notappropriate yet. Therefore, a second main operation is performed on thefirst clock ICLK and the third clock QCLK such that they have a phasedifference of 90 degrees with each other. Consequently, through theabove described first and second main operations, the first to fourthclocks ICLK, QCLK, IBCLK and QBCLK are corrected to quadrature phaseclocks having the phases of 0 degree, 90 degrees, 180 degrees and 270degrees, respectively.

As described above, a phase correction method in accordance with theembodiment of the present invention includes detecting a phasedifference between the first clock ICLK and the second clock IBCLK tocorrect the clocks to have a phase difference of 180 degrees, detectinga phase difference between the third clock QCLK and the fourth clockQBCLK to correct the clocks to have a phase difference of 180 degrees,and detecting a phase difference between the first clock ICLK an thethird clock QCLK to correct the clocks to have a phase difference of 90degrees. As such, the first to fourth clocks ICLK, IBCLK, QCLK and QBCLKmay be corrected to quadrature phase signals having phases of 0 degree,90 degrees, 180 degrees and 270 degrees, respectively.

In more detail, the detecting a phase difference between the first clockICLK and the second clock IBCLK to correct the clocks includes:detecting a rising edge of the first clock ICLK and a rising edge of thesecond clock IBCLK; activating the first edge detection signal I_EDGEand deactivating the second edge detection signal IB_EDGE in response tothe rising edge of the first clock ICLK, and deactivating the first edgedetection signal I_EDGE and activating the second edge detection signalIB_EDGE in response to the rising edge of the second clock IBCLK;comparing logic high level sections of the first edge detection signalI_EDGE and the second edge detection signal IB_EDGE to output thecomparison signals IDCDOUT and IDCDSTB; generating the first delaycorrection codes ICODE<0:N−1>, which are digital codes corresponding tothe comparison signals IDCDOUT and IDCDSTB; and delaying the phases ofthe first and second clocks ICLK and IBCLK in response to the firstdelay correction codes ICODE<0:N−1> so that the first and second clocksICLK and IBCLK have a phase difference of 180 degrees.

Similarly, the detecting a phase difference between the third clock QCLKand the fourth clock QBCLK to correct the clocks includes: detecting arising edge of the third clock QCLK and a rising edge of the fourthclock QBCLK; activating the third edge detection signal Q_EDGE anddeactivating the fourth edge detection signal QB_EDGE in response to therising edge of the third clock QCLK, and deactivating the third edgedetection signal Q_EDGE and activating the fourth edge detection signalQB_EDGE in response to the rising edge of the fourth clock QBCLK;comparing logic high level sections of the third edge detection signalQ_EDGE and the fourth edge detection signal QB_EDGE to output thecomparison signals QDCDOUT and QDCDSTB; generating the second delaycorrection codes QCODE<0:N−1>, which are digital codes corresponding tothe comparison signals QDCDOUT and QDCDSTB; and delaying the phases ofthe third and fourth clocks QCLK and QBCLK in response to the seconddelay correction codes QCODE<0:N−1> so that the third and fourth clocksQCLK and QBCLK have a phase difference of 180 degrees with each other.

Finally, the detecting a phase difference between the first clock ICLKan the third clock QCLK to correct the clocks includes: detectingwhether a phase difference between the first clock ICLK and the thirdclock QCLK is 90 degrees to output detection result signals QPDOUT andQPDSTB; generating the third delay correction codes QPCCODE<0:N−1>,which are digital codes corresponding to the detection result signalsQPDOUT and QPDSTB; and delaying the phases of the first clock ICLK andthe third clock QCLK in response to the third delay correction codesQPCCODE<0:N-1> to generate quadrature phase signals ICLK_O, QCLK_O,IBCLK_O and QBCLK_O.

Since the DDR semiconductor memory device was developed to overcome thelimitation in the clock speed, attempts to improve operating speed of adata processing apparatus such as a semiconductor memory device and aCPU has been focused on inputting/outputting a plurality of data duringone clock cycle. However, such a method may reduce a data valid windowif the phase relations of the reference clocks for inputting/outputtingdata is inaccurate. In such a case, it may be impossible to achieve adesired operation performance of the data processing apparatus.Therefore, the data processing apparatus requires a circuit forcorrecting the phases of the reference clocks. The phase correctioncircuit and method in accordance with embodiments of the presentinvention can correct the quadrature phase clocks so that rising edgesof the quadrature phase clocks are positioned exactly at 0 degree, 90degrees, 180 degrees and 270 degrees, respectively, thereby optimizingoperating speed of the semiconductor memory device and system.

Furthermore, even to the case where the phase intervals are decreasedfurther to output more data, the present invention can be applied. Aclock phase correction method in accordance with the present inventionincludes correcting N pairs of clocks (where, N is a natural numberlarger than 1) such that one clock of each pair has a phase differenceof 180 degrees with the other clock of the pair, and selecting one clockin each pair to correct the selected clocks to have phase differences of360/N degrees with each other, so that all of the clocks are separatedfrom each other by uniform distances.

Specifically, the correcting N pairs of clocks includes: detectingrising edges of two clocks of each pair; generating two signalsactivating in the opposite direction in response to the detected risingedges; comparing logic high level sections of the two signals;generating digital codes corresponding to the comparison results; anddelaying phases of the two clocks in response to the digital codes sothat the two clocks have a phase difference of 180 degrees therebetween.The selecting one clock in each pair to correct the selected clockincludes: selecting one clock in each pair to detect whether theselected clocks have phase differences of 360/N degrees therebetween;generating digital codes corresponding to the detection result; anddelaying phases of the selected clocks in response to the digital codessuch that the selected clocks have phase differences of 360/N degrees.

As described above, the phase correction circuit in accordance with theembodiments of the present invention can correct accurately phasedifferences between quadrature phase clocks in a semiconductor memorydevice and system using the quadrature phase clocks, thereby enhancingreliability in transferring data or signal and securing a stableoperation.

Also, the phase correction circuit performs phase correction operationson the quadrature phase clocks through a sequential step-by-stepprocess, thereby reducing the correction time and the overall currentconsumption.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. A semiconductor memory device, comprising: an edge detectorconfigured to receive two pairs of complementary clocks to detect edgesof the clocks; a comparator configured to compare output signals of theedge detector to detect whether clocks of the same pair have a phasedifference of 180 degrees and detect whether clocks of different pairshave a phase difference of 90 degrees; a control signal generatorconfigured to generate a control signal for controlling phases of thetwo pairs of clocks according to an output signal of the comparator; anda phase corrector configured to correct phases of the two pairs ofclocks in response to the control signal.
 2. The semiconductor memorydevice as recited in claim 1, wherein the edge detector includes: afirst edge detector configured to detect rising edges of one of saidpair of clocks; and a second edge detector configured to detect risingedges of the other of said pair of clocks.
 3. The semiconductor memorydevice as recited in claim 2, wherein the comparator includes: a firstduty comparator configured to compare a duty ratio difference betweenoutput signals of the first edge detector; a second duty comparatorconfigured to compare a duty ratio difference between output signals ofthe second edge detector; and a phase comparator configured to comparean output signal of the first edge detector and an output signal of thesecond edge detector to determine whether the clocks of different pairshave a phase difference of 90 degrees.
 4. The semiconductor memorydevice as recited in claim 1, wherein the control signal generatorgenerates analogue control signals having a voltage level correspondingto output signals of the comparator, and the phase corrector includes avoltage-controlled delay line capable of determining a delay timecorresponding to the analogue control signal.
 5. The semiconductormemory device as recited in claim 1, wherein the control signalgenerator generates digital control signals corresponding to outputsignals of the comparator, and the phase corrector includes a pluralityof shift registers capable of determining a delay time corresponding tothe digital control signals.